With the rapid development of electronic information technology, PCB has developed increasingly towards high density, high reliability, multi-layered, low cost and automatic continuous production, thus higher and higher requirements have been put forward to the heat resistance and reliability of the substrates for PCB. However, since the FR-4 using epoxy resin as the main body has always suffered from the defect of poor high temperature resistance, it has been inadequate for the application requiring high temperature resistance and high reliability of circuits.
Silicone resin is a thermosetting resin, one of its most prominent properties is the excellent stability against thermal oxidation. This is mainly because the skeleton of the silicone resin is Si—O—Si, so its decomposition temperature is high, it can be used under 200-250° C. in the long term without decomposition or discoloration, and it can withstand higher temperatures when coordinated with heat resistant fillers.
Meanwhile, the silicone resin has excellent electrical insulation properties, and since the silicone resin contains no polar groups, its dielectric constant and dielectric loss tangent value vary very little within a wide temperature range and frequency range, and the silicone resin has superior electrical insulation properties at the same time. Due to the carbonizable component of the silicone resin is less, its arc resistance and corona resistance are very prominent as well. Silicone resin has a prominent weather resistance, which is beyond the reach of any kind of organic resins. Even if the silicone resin is irradiated under intense ultraviolet light, it is resistant to yellowing.
At present, in order to impart flame retardancy to laminates, the formulation in combination with the brominated flame retardants is used. However, since recently more and more attentions have been paid to the environmental problems, it is desirable to use the resin compositions containing no halogen compound to further study the phosphorus compounds which can replace the halogen-containing flame retardants. The phosphorus compounds may also produce toxic compounds such as phosphine, etc. when burned, therefore it is desirable to develop a laminate having flame retardancy and a low thermal expansion coefficient even if the halogen compounds and the phosphorus compounds are not used. The silicone resin itself also has very good flame retardancy when no halogen and phosphorus-containing flame retardant is added.
In view of the high heat resistance, halogen-free and phosphorus-free flame retardancy, combined with excellent electrical insulation properties, prominent weather resistance of the silicone resin, meanwhile the completely cured silicone resin also has very low thermal expansion coefficient (<2.0%), its performance will be more excellent when coordinated with functional fillers. Therefore, the laminates prepared with the silicone resin system just meet the market demands for a high heat-resistant, halogen-free and phosphorus-free (high glass transition temperature of >200° C., and low expansion coefficient in the Z-axis of <2.0%) copper foil-clad laminate for high-performance printed circuits.